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Discussion Starter #1
Went to change the plugs in the bike to getter ready to run for the forst time in 8 years and the plug broke off leaving only the threaded body stuck in the head. Any suggestions.
 

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Maybe try and drill out the center of the plug, then use an extractor. Just go slow and make sure to soak the threads with PBblaster for a couple of days before hand.
 

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Hello Jughead,

First off, what make, model, year is the bike.

Second, do you have enough room and did it break where you can get an easy out into it?

Third, do you have any pics?

later...
 

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Discussion Starter #4
1973 Honda CB750 Four k3 is the model. Look at a spark plug, the theaded portion is stuck in the head, the nut portion broke clean off of the threaded portion flush with the head. I've never seen it before. I had put some Liquid wrench on each plug days before, knowing this might be a problem. got two of them out, and they look like the orig plugs, old rusty Champions. The broke off one is in Cyl No. 2. Very difficult to get to. No need to drill a hole, it's already hollow.
 

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If it already has a hole, then just use an extractor bit in a drill and get it out. I had to do the same thing to a screw in my breather cover that one of the previous owners had stripped out.
 

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I don't know if the extractor will work, it would have to be long enough to reach and at that small diameter (@3/8"), I might break the extrator. I will try it. Okay, if that doesn't work, to get the head off, will I need to remove the entire engine, or is there enough clearance under the backbone to take the heads off while the engine is still in the bike? Thanks for all of your input, This is by far the BEST forum. You guys are great.
 

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when you purchase the extractor also purchase a socket that will attach to it. then the extractor, socket, extension, and ratchet will be your best friends...
 

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time to pull the motor out of the frame.

not kidding about that. If it is a SOHC you will save your self so much time an aggravation by jut pulling the motor out and setting it up on the bench. You will not be able to get any tool to do its job right regarding the #2 plug, the stock sparkplug wrench barely fit fer chrissakes.

Once it is out you can try an easy out. Since it is the spark plug hole drilling is out of the question.
 

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Sorry to hear about that - there is no way to pull the head without pulling the engine. Like Geeto says - you'll want to get the head on the work bench to do anything with it. I hate when that happens, next time stick with NGK's
 

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Discussion Starter #11
Thanks guys, I was already planning to take the motor out, knew it would be really aggrevating otherwise. I'll update y'all later, thanks again.

Jug
 

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I was just about to say what Geeto said do not drill. all thos fine little shavings will drop right into you cylinder making another big problem. looks like you best bet is to take the engine out to take the head off but trying the easy out first if you can get it to work wont hurt. good luck bud. wish you the best.
 

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heck I'd drill or break out any brittle stuff inside that prevented getting a bite on it's ID

then use a spline type extractor, with it's corresponding splined nut, they are made by rigid

easy enough to experiment with another broken plug to confirm what you have will fit

it can be done

while drilling or crunching out the center, I'd fill the cylinder with shaving creme

easy enough to do thru intake or exhaust port and when done

blow it out thru the plug hole out either port

the tapered extractors could very easily "swedge" the thin remains of the threaded body tighter into the head

you may also try warming the ferrous metal with a fine tipped torch then chilling it rapidly.... say with ice water

that alone may be enough to allow you to dig it out


another lil tidbit

many gearheads are unaware that sockets actually exist that will couple the square drives found on the end of taps and swedge type extractors

they are called "tap sockets"

round and impact black having an oring internally which cushions brittle taps to help prevent them shattering while being driven by the socket
 

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I am pretty sure you can get at it without taking the head off. The hard part is just getting to that area on a cb750.

removing the head on a cb750 will require you to purchase a new gasket set as well as a new timing chain. The stock chain is an endlesslink chain, meaning it has no master link - it will need to be cut to be removed. If you do decide to do it, do a new base gasket at the cylinder also and the new o-rings in the oil passages, and a new adjuster, etc....
 

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WHAT!! - the head can be removed without cutting the timing chain, remove the gear off the cam and you can thread the cam off the head, just remember to tie a piece of wire on the timing chain so it doesn't fall into the base of the engine. You will need a new head gasket - changing the other gaskets should also be done.

I'm wondering if you can use a dental pick to remove the plug threads without removing the head. If you can get it you in one piece great - if you have bits endup inside the engine then your looking at a tear down. good luck
 

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geets had too much mexican water, or cervezas, or something.


jc
 

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forgot about the cam gear...still that is kind of a pain in the ass operation because you have to strip the valve train (leave the springs and valves but all else has to come out) to remove the cam. I think it may be easier to do a new timing chain than taking the rockers and the cam bearing guides out.
 

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Geeto - don't you have to split the cases and pull the crank to get a new timing chain on????

Oh well since you got it torn down that far, you might as well do a valve job, polish the crank, change out your rod, put in bigger pistons and install a racing cam. And for good measure - add a turbo with nitrous while your at it.....

Funny how a $3.00 plug can cost you 2 grand.
 

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on a cb750 if it can't be fixed with a philips head screw driver or a hammer it is a pain in the ass to me.

yeah that snowball effect is something I was kind of referring to earlier. as long as you need to remove the head, might as well do all the gaskets, as long as the gaskets need doing, might as well do the rings, as long as the rings need doing might as well put in a big bore kit.....and the hits just keep on coming.
 
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